Field of the Disclosure
Embodiments of the present application relate to the art of a driving force control system for a vehicle configured to control a torque distribution ratio to right and wheels.
Discussion of the Related Art
JP-A-2011-163519 describes a yaw moment control device for a vehicle having a differential unit for distributing torque of a prime mover to right and left wheels. According to the teachings of JP-A-2011-163519, the differential unit is provided with a pair of frictional engagement devices for altering a torque split ratio to a right driving wheel and to a left driving wheel. Specifically, torque distributed to the right driving wheel is increased by increasing frictional engagement force of the right frictional engagement device, and torque distributed to the left driving wheel is increased by increase frictional engagement force of the left frictional engagement device. For example, during accelerating the vehicle while turning, the torque distributed to the outer wheel is decreased based on a slip ratio of the outer wheel. By contrast, during decelerating the vehicle while turning, the torque distributed to the inner wheel is increased based on a slip ratio of the inner wheel.
According to the teachings of JP-A-2011-163519, when the differential unit increases torque delivered to one of the driving wheels, the differential unit decreases torque delivered to the other driving wheel. Likewise, when the differential unit decreases torque delivered to one of the driving wheels, the differential unit increases torque delivered to the other driving wheel. In this situation, however, the torque split ratio is controlled based simply on the slip ratio of one of the driving wheels. That is, although the torque of said one of the driving wheels can be optimized, the torque of the other driving wheel may not be controlled properly. For this reason, traveling stability of the vehicle may be degraded if the torque of said other driving wheel is increased or decreased excessively.